A rocket is a vessel that can send you up off of the planet. You sit in a metal pod, on the tip of the rocket, and strap in. At blastoff the rocket blasts from its stand and lifts the pod with it.

The rocket and pod travel up, extra fast, until the rocket's tank is empty. As it runs empty, the rocket will cut off from the pod, but the pod will not stop. It will keep going on the same path it is moving on because of something called inertia. Inertia is what happens when something is moving. It can keep moving until something stops it. The people in the rocket can move the rocket out of its path. That lets them stop inertia so they can come back down to the earth.
(Spache: 4.21)